QuakeScout
Magnitude3.5

Reviewed by USGSAlaska10y ago

M3.5 earthquake 21 km NE of Nikolski, Alaska

Sunday, March 20, 2016, 00:44:52 UTC · 53.078°N, 168.631°W

A magnitude 3.5 earthquake struck 21 km NE of Nikolski, Alaska on Sunday, March 20, 2016, 00:44:52 UTC, at a depth of 93.3 km (intermediate).

Magnitude
3.5
Minor · mb
Depth
93 km
Intermediate
Felt reports
0
Max intensity I
Est. shaking
—
No ShakeMap
PAGER alert
None
Not issued
Tsunami
No flag
USGS feed

Outlined circle: this earthquakeDashed circle: 50 km aftershock search area

In context

How big was it, and why here?

Energy released

3 tons of TNT

That is about 1/5,615 of the Hiroshima bomb. A magnitude 5.0 releases about 178 times more energy.

Tectonic setting

127 km

from the nearest mapped plate boundary, between the North American and Pacific plates. Earthquakes this far from a boundary happen on faults inside a plate, often less frequently but sometimes strongly.

Depth: intermediate

93 km

Intermediate-depth earthquakes usually break inside a plate that is sinking into the mantle. Shaking spreads over a wide area but is gentler at the epicenter than a shallow quake of the same size.

Did You Feel It?

Where it was felt

No “Did You Feel It?” reports have been published for this event yet. If you felt it, you can add your report on the USGS website.

I felt it — report to USGS ↗

USGS PAGER estimate

Who was exposed to shaking

USGS publishes PAGER impact estimates for significant earthquakes, usually within an hour. No PAGER estimate is available for this event.

After the main event

Aftershocks within 50 km

USGS lists 5 M2.5+ earthquakes within 50 km in the following 30 days; the largest was M3.8 on March 22, 2016. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.

M3M41h6h1d3d7d14d30dMainshock M3.5
Time after the mainshock on a logarithmic scale (first hours stretched), magnitude on the vertical axis. M2.5+ events from USGS.
  1. 2.738 km ESE of Nikolski, Alaska10y ago · 38 km SE of this epicenter
  2. 2.53 km SSE of Nikolski, Alaska10y ago · 23 km SW of this epicenter
  3. 3.831 km NE of Nikolski, Alaska10y ago · 9 km NE of this epicenter
  4. 2.630 km ESE of Nikolski, Alaska10y ago · 26 km SE of this epicenter
  5. 2.643 km ESE of Nikolski, Alaska10y ago · 43 km SE of this epicenter

Regional history

Past M5+ earthquakes within 300 km

USGS lists 615 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:

  1. 7.8234 km SSW of Nikolski, AlaskaMarch 7, 1929 · 254 km S of this epicenter
  2. 7.881 km E of Nikolski, AlaskaJuly 2, 1965 · 66 km E of this epicenter
  3. 7.4133 km WNW of Nikolski, AlaskaApril 18, 1916 · 141 km W of this epicenter
  4. 7.3Fox Islands, Aleutian Islands, AlaskaJune 24, 2011 · 245 km SW of this epicenter
  5. 7.139 km S of Akutan, AlaskaMarch 22, 1957 · 205 km NE of this epicenter
  6. 7.135 km SW of Nikolski, AlaskaMarch 11, 1957 · 57 km SW of this epicenter

History · NOAA

Deadliest earthquakes in this area

NOAA’s significant-earthquake database lists 13 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:

  1. 1901M7.8

    Aleutian Islands: Fox Islands

    31 Dec 1901 · 243 km away

    Limited damage (under $1M)tsunami

  2. 1965M6.5

    Aleutian Islands: Fox Islands

    2 Jul 1965 · 72 km away

    Limited damage (under $1M)tsunami

  3. 1917M7.9

    Alaska Peninsula

    31 May 1917 · 193 km away · intensity V

  4. 1902M7.8

    Aleutian Islands: Fox Islands

    1 Jan 1902 · 107 km away

  5. 1907M7.8

    Aleutian Islands

    2 Sep 1907 · 92 km away

  6. 1929M7.8

    Aleutian Islands: Fox Islands

    7 Mar 1929 · 249 km away · intensity V

    tsunami

NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.

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